Field of Invention
The invention relates to a process for the stabilizing of thermoplastic polyurethanes.
Thermoplastic polyurethanes are commonly prepared in particulate form for use in thermoforming operations. Sometimes the particles or granules of the polyurethane are dissolved in a solvent and the resultant solution used in paints or varnishes or for casting of films.
However carefully the manufacture of thermoplastic polyurethane granules is carried out, the product frequently tends to undergo significant change on aging. It is an object of this invention to treat thermoplastic polyurethane in a particulate solid state so as to stabilize it against substantial change in its properties on aging.
The invention also relates to a process for altering the characteristics of thermoplastic polyurethane thermosets.
Some thermoplastic polyurethanes are so formulated that after being formed, they can be heated to convert them to thermoset polymers. It sometimes happens, however, that such thermoplastic polyurethane thermosets have desirable properties for solution applications in which the thermosetting characteristic is undesirable. It is an object of the invention therefore to treat thermoplastic polyurethane thermosets to destroy the thermosetting character thereof without substantially altering the properties of the thermoplastic polyurethane thermoset which make it desirable for solution applications.